An electric compressor has a cylindrical housing that accommodates a compression mechanism and a motor for driving the compression mechanism. Various devices having a cylindrical housing have been provided. For example, PTL 1 discloses a flanged-type motor having a flanged bearing bracket on the load side. Furthermore, PTL 2 discloses a vane pump having a pump housing. Furthermore, PTL 3 discloses a screw compressor (fluid machine) having a hollow screw rotor.
With regard to these patent literatures, PTL 1 discloses a configuration for machining a flange face of the bearing bracket, in which trapezoidal chucking bases projecting in a belt-like shape along the axial direction are provided with equal intervals, at intermediate positions of attaching portions provided at three positions in the circumferential direction on the outer circumferential surface of the bearing bracket, in order to allow machining thereof by being held by a chuck of a machining apparatus. Furthermore, PTL 2 discloses a configuration in which chucking surfaces having parallel side surfaces and end surfaces are provided at two positions at intermediate positions of attaching boss portions which are provided at four positions on the outer circumference of a pump housing in order to enable machining by chucking the side surfaces.
Furthermore, PTL 3 discloses a configuration in which straight portions that allow a rotor to be chucked during machining are formed on the inner circumferences of openings in three tooth traces (tooth forms and hollow portions), provided with equal intervals at an angle of 120 degrees to one another, of a male screw rotor in order to allow these straight portions to be chucked by three chucking tools during machining.